The rise of the Internet has led to the development of a vast number and variety of electronic services, including Web services that help users communicate with each other, better organize their lives, access and store electronic information, and improve work productivity. Web services accessible across the Internet include communications services (e.g., e-mail and instant messaging services), services that enhance personal organization and time management (e.g., calendar services and address book services), financial services (e.g., online banking and online investing services) and business specific services (e.g., a document organization and management services tailored to a specific company).
When a user wishes to access an electronic service, the user typically sends a service request to a provider of the electronic service. The electronic service provider receives the service request, authenticates the user (i.e., determines that the user is, in fact, who he or she purports to be), and determines whether the user is authorized to access or invoke the requested electronic service. If the user is so authorized, the electronic service provider enables the user to access the requested service.